1. Field of the Invention
This invention is related to a spandex fiber which is protected by a combination of phenolic and phosphitic antioxidants against discoloration due to heat and/or atmospheric smog. In particular the invention concerns such spandex fiber which has improved resistance to heat and smog provided by an antioxidant combination that includes a particularly effective type of phosphitic antioxidant.
2. Description of the Prior Art
Spandex fibers are well known in the art. Such fibers, especially polyether-based spandex fibers are known to discolor upon heating and/or upon prolonged exposure to atmospheric smog. Many agents have been suggested in the art to combat these discoloration problems. These include combinations of phenolic and phosphitic additives, such as those disclosed in Bell et al., U.S. Pat. No. 3,386,942 and Megna et al., U.S. Pat. No. 3,573,251. Although many such combinations of agents have been suggested, few, if any, have been utilized commercially with spandex fibers. Further improvements in the resistance of spandex fibers to discoloration are still desired to enhance the utility of the fibers in many end uses.
In seeking a solution to the above-described problem, the present inventor found that when conventional hindered phenolic antioxidants are used in spandex fibers with a particular type of phosphitic antioxidants, selected from the many known types of phosphitic antioxidants, the resistance of the fibers to discoloration is surprisingly much greater than when the fibers contain the additive combinations disclosed in the art.